The primary source of frictional loss in a vane pump, whether it is a fixed or variable displacement type, is friction between its vane tips and a mating inner surface of its stationary cam ring. This frictional loss manifests itself as generated heat that transfers directly into pumped fluid. In aeronautical applications, a vane pump may serve as a fuel pump for a gas turbine engine, in which case the pumped fuel may serve as a heat sinking cooling medium for auxiliary systems, such as lubrication systems, fuel powered actuation systems and electronic control systems. Transfer of generated heat to the fuel due to frictional loss in the pump reduces the heat sink capacity of the fuel for cooling such auxiliary systems.
One type of vane pump overcomes such vane-cam ring frictional loss to some degree by forming the outer surface of the cam ring into a journal that fits in a bearing. The bearing pivots about a pin attached to a housing for the pump to allow variable displacement of the pump. However, the relatively large surface area of the journal bearing still induces significant frictional loss.